It is well known to provide electronic communications equipment in which circuit cards are removably connected to a backplane, the circuit cards being arranged parallel to one another and being guided in shelves to be perpendicular to the backplane, with electrical connections being established between connectors on the backplane and complementary connectors on the back edge of each circuit card. Typically, the connectors are constituted by multiple pins and sockets arranged in one or more lines (inline connectors) along part or all of the back edge of the circuit card. When a circuit card is inserted into the equipment, the shelf guides provide an approximate alignment for the pins and sockets, and a precise alignment is achieved by surrounds around the pins and sockets.
There is an increasing need in the communications industry to communicate signals, for example at radio frequencies above about 5 MHz, via coaxial cables. As is well known, a coaxial cable consists of a central conductor and a surrounding shield which is grounded to prevent radiation of a signal from the central conductor. Coaxial connectors, providing for connections between a coaxial cable and another coaxial cable or conductors on a circuit card while maintaining continuity of the shield and a desired characteristic impedance of the cables to avoid signal reflections, are also well known.
It is desirable to provide coaxial connections between circuit cards and a backplane in a similar manner to the in-line connectors referred to above, using conventional coaxial connectors. However, this presents a serious problem in that conventional coaxial connectors allow for very little mechanical misalignment. Providing the necessary mechanical alignment for one or more coaxial connectors, on a circuit card which also provides other, coaxial and/or in-line, connectors, with complementary connectors on the backplane requires close tolerances which can not reasonably be met in manufacture. This problem increases with increasing sizes of circuit card and increasing distances between the connectors.
An object of this invention, therefore, is to provide a backplane assembly, including a plurality of connectors at least one of which is a conventional coaxial connector, which avoids or eliminates this problem.